This invention relates generally to the testing of electronic modules, and more particularly to a high speed pass through test system and test method for testing electronic modules.
Electronic modules, such as semiconductor memory modules, multi chip modules, semiconductor carriers, semiconductor packages, and microprocessors are routinely tested during manufacture. The modules include terminal contacts in electrical communication with the electronic devices contained on the modules. For performing various test procedures on the modules, temporary electrical connections are made to the terminal contacts.
One type of prior art electronic module 10, which is illustrated in FIGS. 1A and 1B, includes a substrate 12, and multiple semiconductor packages 16 mounted to the substrate 12. The module 10 also includes a row of terminal contacts 14 on the substrate 12 in electrical communication with the integrated circuits contained on the semiconductor packages 16. The terminal contacts 14 comprise generally planar, in-line metal pads located on opposing sides of the substrate 12 along a lateral edge 18 thereof. The substrate 12 typically comprises an electrically insulating material such as a glass filled plastic (FR-4), or a ceramic. In addition, the substrate 12 includes through openings 19 which facilitate indexing and handling by automated test equipment and carriers.
For testing the electronic module 10, test systems have been developed and are commercially available from various manufacturers. These test systems are configured to make temporary electrical connections with the terminal contacts 14 on the module 10. In addition, the test systems are configured to apply test signals through the terminal contacts 14 to the electronic devices on the module 10, and then to analyze the response signals from the electronic devices. Often times these test systems merely test the gross functionality of the module 10, as the semiconductor packages 16 on the module 10 have been previously individually tested and burned-in.
The test systems typically include test boards and test circuitry in electrical communication with the test boards. In addition, the test boards typically include interface boards having test contactors configured to physically and electrically engage the terminal contacts 14 on either side of the module 10. In general, there are two types of test systems, which are sometimes referred to as xe2x80x9cpass through test systemsxe2x80x9d, or xe2x80x9csocket test systemsxe2x80x9d.
FIG. 1C illustrates a pass through test system 11PT having an interface board 13PT, and test contactors 15PT on the interface board 13PT. The test contactors 15PT are in electrical communication with test circuitry (not shown). In addition, the test contactors 15PT are movable from an inactive (open) position in which the terminal contacts 14 on the module 10 are not engaged, to an active (closed) position in which the terminal contacts 14 on the module 10 are physically and electrically engaged.
As shown in FIG. 1C, with the test contactors 15PT in an inactive (open) position, the module 10 can be indexed into a contactor area between the test contactors 15PT, as indicated by arrow 17PT. With the module 10 located in the contactor area, the test contactors 15PT can be mechanically moved to the active (closed) position to physically and electrically engage the terminal contacts 14. The pass through test contactors 15PT are sometimes referred to as being xe2x80x9czero insertion forcexe2x80x9d (ZIF) contactors because temporary electrical connections can be made without an insertion force being placed on the module 10.
FIG. 1D illustrates a socket test system 11S having an interface board 13S, and test contactors 15S on the interface board 13S. In this case, the test contactors 15S are normally in an active (closed) position, but are mechanically moved to an inactive (open) position as the module 10 is inserted from above, as indicated by arrow 17S. When the module 10 is in place, the test contactors 15S move back to the active (closed) position to physically and electrically engage the terminal contacts 10. The socket test contactors 15S are sometimes referred to as being xe2x80x9clow insertion forcexe2x80x9d (LIF) contactors because an insertion force is exerted on the module 10 in making the temporary electrical connections with the test contactors 15S.
One advantage of the pass through test system 11PT (FIG. 1C) over the socket test system 11S, is that no insertion forces are exerted on the module 10 to provide electrical engagement for testing. Accordingly, less physical stress is placed on the module 10 during testing with the pass through test system 11PT. Also, as the number of terminal contacts 14 on the module 10 increases, the insertion forces exerted by the socket test system 11S increase. The socket test system 11S can therefore damage the module 10, or the terminal contacts 14 on the module 10, and can be more expensive to operate and maintain.
The present invention is directed to an improved pass through test system. In pass through test systems it is desirable to make temporary electrical connections with the terminal contacts 14 on the modules 10 that are reliable, and have low electrical resistance. This requires that the terminal contacts 14 be scrubbed, or alternately penetrated by the test contactors 15PT, such that oxide layers and surface contaminants on the terminal contacts 14 do not adversely affect the temporary electrical connections. However, in scrubbing or penetrating the terminal contacts 14, damage to the terminal contacts 14 and modules 10 must be minimized.
It is also advantageous in pass through test systems for the temporary electrical connections to provide electrical paths that are short in length to facilitate the application of high speed test signals, and to prevent capacitive coupling and the introduction of noise and spurious signals. Further, it is advantageous to make, and then break, the temporary electrical connections as quickly as possible, to facilitate a high throughput for the test procedure.
The pass through test system of the invention includes test contactors configured to make temporary electrical connections that are reliable, have low electrical resistance, and minimally damage terminal contacts on the modules. In addition, the test contactors are relatively inexpensive to make, provide a high throughput, and can be operated in a production environment with minimal maintenance.
In accordance with the present invention, a pass through test system and test method for testing electronic modules are provided. In illustrative embodiments, the test system is configured for testing electronic modules having planar, in-line terminal contacts substantially as previously described.
The test system includes test circuitry configured to generate test signals, and an interface board having interface contacts, and high speed conductors, in electrical communication with the test circuitry. The interface board can be mounted to an automated or manual test handler configured to transport, align, and hold the module on edge, generally parallel to the interface board.
The test system also includes test contactors configured to engage the terminal contacts on the component, and to simultaneously engage the interface contacts on the interface board. In illustrative embodiments, the test contactors comprise fret contacts configured to engage the terminal contacts with a zero insertion force (ZIF) on the module. An actuator mechanism moves the test contactors from an inactive (open) position wherein neither the terminal contacts on the module, nor the interface contacts on the interface board are engaged, to an active (closed) position wherein both the terminal contacts and the interface contacts are electrically engaged.
During electrical engagement of the terminal contacts, the interface contacts electrically engage the test contacts at an intermediate point along a length thereof, such that the electrical paths through the test contactors to the high speed conductors on the interface board are shortened. The interface contacts can comprise conductive polymer bumps, or alternately fret-type contacts. In addition, the high speed conductors on the interface board can have a multi level, or interleaved configuration to provide an increased density and impedance adjustment.
The test method includes the steps of: providing an interface board comprising a plurality of interface contacts and high speed conductors in electrical communication with test circuitry; providing a plurality of movable test contactors comprising fret contacts configured to electrically engage the terminal contacts and the interface contacts with a zero insertion force on the module; placing the module edge to edge and generally parallel to the interface board; moving the test contactors to electrically engage the terminal contacts on the module and the interface contacts on the interface board; and then applying test signals through the interface contacts, the test contactors and the terminal contacts to the module.